But as appealing as opiates are as a poison, the symptoms didn’t match the victim in my novel. I then searched poisonous plants in England, picking through foxglove, hemlock, yew tree berries, wolfsblane, deadly nightshade, and cuckoo pint. Again, all the symptoms were too sudden, and killed the victim too quickly.

The symptoms of low levels of arsenic poisoning are headaches, confusion, drowsiness, and diarrhea. Higher quantities result in vomiting blood, cramping muscles, hair loss, and convulsions, before coma and death. And according to Patient Info, a person poisoned with arsenic has a garlicky smell on their skin and breath.

In the Victoria era, arsenic formed part of a beauty product known (in the USA) as “Arsenic Complexion Wafers” which promised to get rid of unsightly pimples. Arsenic poisoning has similar symptoms to cholera, and was often used in the Middle Ages and Renaissance periods to murder people without being caught. By the early 19th Century, this was so common, that arsenic gained the nickname “inheritance powder” due to persistent rumours that it was used by impatient heirs to speed up the death of their rich relatives.